Problem Solving Strategies

Prateek Mourya

05:37

Sir now i understand why you cant play games now

John Rennie

@PrateekMourya Play games?

Prateek Mourya

Yes video games

Judging by your thumb

John Rennie

I'm just old, and everyone's hands get a bit arthritic as they get old :-)

Prateek Mourya

Your age?

John Rennie

I'll be 60 in February.

8

user586228

06:10

@JohnRennie Seems too many people are interested to know your age

LOL

John Rennie

I think it's natural to be curious about the people you meet on the Internet :-)

5

It's very different to meeting people in person.

user586228

Very true...

Can you help me to calculate Tb from this equation

John Rennie

user586228

Btw @JohnRennie If it is not so personal where do you work professionally?

John Rennie

I'm retired.

user586228

06:12

Where did u used to work other than Unilever as a colloidal scientist

napstablook

@JohnRennie haha that is so true!

John Rennie

After I left Unilever I moved into IT. I became a network manager i.e. running the servers and the network for a company.

user586228

Anyway .... How to calculate $T_{b}$ from here?

Can u move to IT engineering after PhD in Material Science and Engineering?

napstablook

@JohnRennie which of them did you personally find more interesting?

John Rennie

If you work in science you do lots of computing so scientists generally end up pretty skilled at using computers. We're also pretty good at learning stuff. If you want to switch from science to an IT job it's usually easy to do this.

napstablook

06:15

and which one erm . . .more financially stable

John Rennie

@napstablook Both were a lot of fun in their different ways, and both paid well enough for me to retire at 60 :-)

2

user586228

Sounds great

@JohnRennie Can u help me slightly about the problem..I posted..

Did I ask the doubt properly?

John Rennie

@user586228 you just posted the solution, not the question ...

user586228

Actually I donot understand how to calculated $T_{b}$ from the solution

Actually I am asking you how to solve the stated equation..

John Rennie

Hmm, yes, I can't see how to rearrange that into an equation for $T_b$. I guess it was solved numerically.

user586228

06:25

Any approximatons that come to your mind

user586228

06:44

@JohnRennie For numerical solution how do I solve it

Any preferred method?

John Rennie

@user586228 I would use a spreadsheet and do a successive approximation

user586228

Ok

How did they calculate $n_{Ag}$

John Rennie

How are you managing to get such badly formatted pictures?

user586228

Actually I am cropping the screenshot

And posting it on MSpaint

Any better technique is welcome

John Rennie

That is what I would do, but after you paste into MSPaint you can crop the image to remove all white space.

napstablook

06:51

you can download lightshot app and upload screenshots its very straight forward

user586228

I could not get u..Can u slightly elaborate

John Rennie

user586228

ok then

John Rennie

Click on the Select tool, then draw a box around the bit if the image you want. Like I've shown.

Then click on Crop where I have highlighted in red.

This removes everything outside the box.

So now it looks like this. The picture contains just the bit you actually want, and not all that white space.

user586228

got u it worked

Now how do you calculated nAr?

calculate*

John Rennie

07:04

@user586228 nAr is just the number of moles of argon, and you are told that one mole is used, so nAr = 1

user586228

Sorry I did not read the question well

extremely juvenille of me..

You might delete this to trash if you want

John Rennie

It's OK :-)

Aridhan

17:29

@JohnRennie sir @satan29 @Satwik @ScientistSmithYT

i need help in understanding orbitals.

I am getting very confused

0

Q: What does orbital mean, exactly?

My teacher told me that orbital is the probability distribution data of the electron around nucleus which is amplitude data in a way. An example of how my teacher actually told what it means involves that you know three possibilities for a coin flip to get head and tail. Therefore, this table is ...

John Rennie

@Aridhan hi :-)

What is confusing you about orbitals?

Aridhan

17:52

Yes

i have written three definitions in my questions

1 by my teacher and 2 from book

they all look to mean different things @JohnRennie

Please help me

John Rennie

@Aridhan the key to understanding this is that quantum objects like electrons are not like little balls whizzing around the atom.

An electron is more like a fuzzy cloud.

Aridhan

Ok.Sir

@JohnRennie

My sir tells me that orbital is this

John Rennie

If you look at a cloud in the sky then it doesn't have a single position. Instead it is spread out over a region of space, and the edges of the clouds are fuzzy and not well defined.

Well an electron is just like this.

Aridhan

Ok.Then how can we say that electron position can be found

if it is a cloud right sir

John Rennie

A 1s electron in a hydrogen atom isn't a point particle occupying an orbital, the 1s orbital is the shape of the cloud that is the electron.

napstablook

17:57

@JohnRennie can you prove that f(2x)=f(x).e^x is only satisfied by f(x)=k.e^x ?

or prove this wrong?

Aridhan

OMG

John Rennie

@napstablook no. Next question? :-)

Aridhan

@JohnRennie OK

John Rennie

@Aridhan I know it seems weird, but this really is true.

napstablook

Oof

Aridhan

17:58

You mean to say that sir electron shape is orbital

John Rennie

@Aridhan yes.

Aridhan

1s is shape of electron

Omg

John Rennie

Yes, the electron is spread out ina clud centred on the nucleus, and the orbital tells you the shape of the cloud.

Aridhan

Then , do electron revolve @JohnRennie

Around nucleus

John Rennie

The cloud can spin, for example in the 2p state the electron cloud has a non-zero angular momentum.

Aridhan

18:00

Of electron can spin

then its probability changes every second

we can’t find its probability then since it is always moving

John Rennie

Remember that the electron is not a little ball, and doesn't spin in the way we can make a cricket ball spin.

Aridhan

Ok.Can we also say that the cloud doesn’t separate from each other

which is electron

John Rennie

> Can we also say that the cloud doesn’t separate from each other

I'm not sure what that means.

Aridhan

Ok.@JohnRennie sir

what I mean is

like cloud is very light right

it like a gas

solid metal cannot be separated from itself like in two pieces since it very stormg

John Rennie

The total mass of a cloud could be quite large, but the cloud is spread out over a large regionso the density at any point can be quite low.

Aridhan

18:02

electron is a cloud

Then what do we mean by finding the probability of electron at that region

John Rennie

Are you asking if we could split the cloud in two and therefore split an electron in two?

Aridhan

Yes

John Rennie

The answer is no, because when we interact with the electron e.g. fire another particle at it, then that interaction does happen at a point.

It's like the cloud gathers itself together at a point to interact with whatever we are firing at it.

Aridhan

Ok

John Rennie

When people talk about the position of the electron, they really mean the position where the interaction with the electron took place.

Aridhan

18:05

then what do we mean by finding the probability of elector.

We already know it’s shape

it is right there present

John Rennie

It's just the density of the cloud.

Where the electron cloud is dense the electron is more likely to interact with something.

Aridhan

Interaction of electron with what sir

ok

John Rennie

Anything. We could fire another electron at it to try and make a collision between the two ...

Aridhan

Let us say we have 1s orbital

sir

John Rennie

OK ... ?

Aridhan

18:06

then , is it that at some region it more dense and some not

or is it equally dense

John Rennie

Yes, the 1s orbital has an equation that says how it varies with distance from the nucleus. If you give me a moment I'll look it up ...

Aridhan

Omg thank you so much

John Rennie

@Aridhan This web page gives you the equations for some of the orbitals

Aridhan

Ok sir

just on more thing

John Rennie

That's the 1s orbital.

Aridhan

18:09

Ok.

But I don’t know how to understand it

I am also preparing for JEE

John Rennie

In that equation r is the distance from the nucleus. a is a constant called the Bohr radius.

Aridhan

ok.

John Rennie

You don't need to know this stuff for the JEE.

Aridhan

That is what sir

I hate jee

I like to be conceptually strong

it only needs you to be able to solve questions

John Rennie

You may get questions on the basic shapes of the orbitals, but you don't need this level of detail.

Aridhan

18:12

Ok.There is n which is principal quantum number which defines K , L ,M and N shell right

if n = 1 m then it is K she’ll

John Rennie

Yes

Aridhan

thereafter

we meet azimuthal quantum number

We make a line between two fumbles

dumbles

we say , that at that line

John Rennie

"dumbbells"

Aridhan

probability of electron is 0

How do we send image.I don’t see option here

dumbbell is like orbital shape

John Rennie

Yes, the p orbitals have a nodal plane i.e. plane where the wavefunction is zero.

Aridhan

18:14

How can at a line probability be zero

like electron is a cloud

John Rennie

If we go back to my analogy of a cloud, then in this plane the density of the cloud is zero.

Aridhan

It is like

there are two cloud

which are separated by a line

John Rennie

Well, the cloud has two lobes, either side of the nodal plane.

Aridhan

Sir.I don’t see option of sending photos here

I would send you a photo of what I think of a shape of electron as and the orbital

John Rennie

@Aridhan Are you on a phone?

Aridhan

18:16

No , iPad

Is it that I can’t

I only see send option

not upload

John Rennie

The option to upload a photo only appears on the desktop site, and you need a certain reputation to use it - I don't know what that number is.

Aridhan

Ohk.That is bad

John Rennie

If you can't see the "upload" button then either you're using the mobile site or you don't have a high enough rep to upload photos.

I need to go now I'm afraid.

I'm here in the morning, from about 05:30 to 12:30 UK time.

That's from 11:00 a.m. Indian time.

Bye :-)

Aridhan

Ok

Thank you very mich

you must rest

thank you for getting up still

Aridhan

18:31

@napstablook can I ask a question to you sir

napstablook

I'm a high school student you don't need to address me as sir. :)

Aridhan

Oh

can you tell me bro that when we apsayp

Say

about finding the probability of electron being present there

dors it mean how u NC dense it is there

NC= much

napstablook

@Aridhan i didnt get the last statement

Aridhan

How much dense is the cloud

that is electron

does that mean the probability of finding electron at a particular point

I hope you understood @napstablook

napstablook

I can't be too specific about details but in atomic structure chapter it was told that the electron cloud's density represents the magnitude of probability of finding the electron at that point in space.

i.e. the denser the cloud at a region the higher the probability of the electron being there.

Aridhan

18:43

Ok

How is your jee preparation going @napstablook

Which year is your jee

napstablook

this is my final year (god knows how many times i had revised these chapters)

anyways i should be going. . . good luck in your prep and goodnight.

user102532

Hi guys

Aridhan

What does it mean by energy of electron

it is cloud right

Transcript for

Problem Solving Strategies